CAIRO — When a Saudi F-15 warplane takes off from King Khalid air base in southern Saudi Arabia for a bombing run over Yemen, it is not just the plane and the bombs that are American.

American mechanics service the jet and carry out repairs on the ground. American technicians upgrade the targeting software and other classified technology, which Saudis are not allowed to touch. The pilot has likely been trained by the United States Air Force.

And at a flight operations room in the capital, Riyadh, Saudi commanders sit near American military officials who provide intelligence and tactical advice, mainly aimed at stopping the Saudis from killing Yemeni civilians.

American fingerprints are all over the air war in Yemen, where errant strikes by the Saudi-led coalition have killed more than 4,600 civilians, according to a monitoring group. In Washington, that toll has stoked impassioned debate about the pitfalls of America’s alliance with Saudi Arabia under Crown Prince Mohammed bin Salman, who relies on American support to keep his warplanes in the air.

Saudi Arabia entered the war in 2015, allying with the United Arab Emirates and a smattering of Yemeni factions with the goal of ousting the Iran-allied Houthi rebels from northern Yemen. Three years on, they have made little progress. At least 60,000 Yemenis have died in the war, and the country stands on the brink of a calamitous famine.

For American officials, the stalled war has become a strategic and moral quagmire. It has upended the assumptions behind the decades-old policy of selling powerful weapons to a wealthy ally that, until recently, rarely used them. It has raised questions about complicity in possible war crimes. And the civilian toll has posed a troubling dilemma: how to support Saudi allies while keeping the war’s excesses at arm’s length.

In interviews, 10 current and former United States officials portrayed a troubled and fractious American response to regular reports of civilians killed in coalition airstrikes.

The Pentagon and State Department have denied knowing whether American bombs were used in the war’s most notorious airstrikes, which have struck weddings, mosques and funerals. However, a former senior State Department official said that the United States had access to records of every airstrike over Yemen since the early days of the war, including the warplane and munitions used.

At the same time, American efforts to advise the Saudis on how to protect civilians often came to naught. The Saudis whitewashed an American-sponsored initiative to investigate errant airstrikes and often ignored a voluminous no-strike list.

“In the end, we concluded that they were just not willing to listen,” said Tom Malinowski, a former assistant secretary of state and an incoming member of Congress from New Jersey. “They were given specific coordinates of targets that should not be struck and they continued to strike them. That struck me as a willful disregard of advice they were getting.”

Yet American military support for the airstrikes continued.

While American officials often protested civilian deaths in public, two presidents ultimately stood by the Saudis. President Obama gave the war his qualified approval to assuage Saudi anger over his Iran nuclear deal. President Trump embraced Prince Mohammed and bragged of multibillion-dollar arms deals with the Saudis.

As bombs fell on Yemen, the United States continued to train the Royal Saudi Air Force. In 2017, the United States military announced a $750 million program focused on how to carry out airstrikes, including avoiding civilian casualties. The same year, Congress authorized the sale of more than $510 million in precision-guided munitions to Saudi Arabia, which had been suspended by the Obama administration in protest of civilian casualties.

Nearly 100 American military personnel are advising or assisting the coalition war effort, although fewer than 35 are based in Saudi Arabia.

American support for the war met stiff headwinds this fall, when congressional fury over the murder of the Saudi dissident Jamal Khashoggi combined with worries over civilian deaths in Yemen.

In response, the Trump administration endedAmerican air-to-air refueling of coalition warplanes over Yemen in November but has otherwise continued to support the war. This month, the Senate voted to end American military assistance to the war altogether, a sharp rebuke to the Trump administration, but the bill died when the House refused to consider it.

The civilian toll is still rising. According to the Armed Conflict Location and Event Data Project, November was the most violent month in Yemen since the group began tracking casualties in January 2016. There were 3,058 war-related fatalities in November, it said, including 80 civilians killed in airstrikes.

‘Expensive Paperweights’

Image

A factory damaged during airstrikes and fighting in Yemen, where a Saudi-led coalition has killed thousands of civilians in a campaign against Houthi fighters.CreditAgence France-Presse — Getty Images

For decades, the United States sold tens of billions of dollars in arms to Saudi Arabia on an unspoken premise: that they would rarely be used.

The Saudis amassed the world’s third-largest fleet of F-15 jets, after the United States and Israel, but their pilots almost never saw action. They shot down two Iranian jets over the Persian Gulf in 1984, two Iraqi warplanes during the 1991 gulf war and they conducted a handful of bombing raids along the border with Yemen in 2009.

The United States had similar expectations for its arms sales to other Persian Gulf countries.

“There was a belief that these countries wouldn’t end up using this equipment, and we were just selling them expensive paperweights,” said Andrew Miller, a former State Department official now with the Project on Middle East Democracy.

Then came Prince Mohammed bin Salman.

When the prince, then the Saudi defense minister, sent fighter jets to Yemen in March 2015, Pentagon officials were flustered to receive just 48 hours notice of the first strikes against Houthi rebels, two former senior American officials said. American officials were persuaded by Saudi assurances the campaign would be over in weeks.

But as the weeks turned to years, and the prospect of victory receded, the Americans found themselves backing a military campaign that was exacting a steep civilian toll, largely as a result of Saudi and Emirati airstrikes.

American military officials posted to the coalition war room in Riyadh noticed that inexperienced Saudi pilots flew at high altitudes to avoid enemy fire, military officials said. The tactic reduced the risk to the pilots but transferred it to civilians, who were exposed to less accurate bombings.

Coalition planners misidentified targets and their pilots struck them at the wrong time — destroying a vehicle as it passed through a crowded bazaar, for instance, instead of waiting until it reached an open road. The coalition routinely ignored a no-strike list — drawn up by the United States Central Command and the United Nations — of hospitals, schools and other places where civilians gathered.

At times, coalition officers subverted their own chain of command. In one instance, a devastating strike that killed 155 people in a funeral hall was ordered by a junior officer who countermanded an order from a more senior officer, a State Department official said.

The Americans offered help. The State Department financed an investigative body to review errant airstrikes and propose corrective action. Pentagon lawyers trained Saudi officers in the laws of war. Military officers suggested putting gun cameras on Saudi and Emiratis warplanes to see how strikes were being conducted. The coalition balked.

In June 2017, American officials extracted new promises of safeguards, including stricter rules of engagement and an expansion of the no-strike list to about 33,000 targets — provisions that allowed the secretary of state, then Rex W. Tillerson, to win support in Congress for the sale of more than $510 million in precision-guided munitions to the kingdom.

But those measures seemed to make little difference. Just over a year later, in August 2018, a coalition airstrike killed at least 40 boys on a packed school bus in northern Yemen.

Still, American leaders insisted they need to keep helping the Saudi coalition.

America’s role in the war was “absolutely essential” to safeguard civilians, the general in charge of Central Command, Gen. Joseph L. Votel, told a charged Senate hearing in March.

“I think this does give us the best opportunity to address these concerns,” he said.

What the U.S. Knows

Image

President Trump, meeting with Crown Prince Mohammed bin Salman of Saudi Arabia in March, bragged of American arms sales to the kingdom.CreditDoug Mills/The New York Times

In March, Prince Mohammed paid a visit to Washington, where he was feted by President Trump. As the two leaders sat in the White House, Mr. Trump held aloft a chart with price-tagged photos of warplanes and other weapons.

But in Congress, the mood was souring. In the March hearing, senators accused the Pentagon of being complicit in the coalition’s errant bombing, and pressed its leaders on how directly the United States was linked to atrocities.

General Votel said the military knew little about that. The United States did not track whether the coalition jets that it refueled carried out the airstrikes that killed civilians, he said, and did not know when they used American-made bombs. At a briefing in Cairo in August, a senior United States official echoed that assessment.

“I would assume the Saudis have an inventory system that traces that information,” said the official, who spoke anonymously to discuss diplomatically sensitive relations. “But that’s not information that is available to the U.S.”

At the coalition headquarters in Riyadh, he said, American liaison officers had access to a database that detailed every airstrike: warplane, target, munitions used and a brief description of the attack. American officials frequently emailed him copies of a spreadsheet for his own work, he said.

The data could easily be used to pinpoint the role of American warplanes and bombs in any single strike, he said. “If the question was “Hey, was that a U.S. munition they used?” You would know that it was,” he said.

Capt. Bill Urban, a spokesman for Central Command, did not deny the existence of the database, but said that American officers only used coalition data to carry out their core mission: advising on civilian casualties, sharing intelligence on Houthi threats and coordinating the midair refueling that ended in November.

“I will not speculate on how the United States could have used or compiled the information the Saudi-led coalition shared for some other function,” he said in a statement. “That is not the mission these advisers were invited to Riyadh to perform. That is not the way partnerships work.”

Other officials have said that collating information about use of American munitions in Yemen would be onerous and, ultimately, pointless. “What difference would it make?” the senior United States official in Cairo said.

Under American law, customers of American weapons must follow the laws of armed conflict or future sales may be blocked, said Ryan Goodman, a former Defense Department attorney who teaches law at New York University.

Mr. Lewis, who left the State Department in 2017, said that in his experience, individual Saudi officers were often concerned or distressed by airstrikes that killed civilians but there was little institutional effort to reform the system.

The Joint Incidents Assessment Team, the body set up to investigate errant strikes, worked diligently at first, he said. But when its findings were made public, the Saudi Ministry of Foreign Affairs had removed any references that were critical of coalition actions.

Asked if that was the case, the Saudi ambassador to Yemen, Mohamed Al Jaber, said, “The JIAT is an independent team,” and he referred any questions to them.

Applying Leverage

Image

Mourners carried the coffin of the mayor of Sana, the Yemeni capital, who was killed in 2016 by an airstrike that hit a different funeral.CreditKhaled Abdullah/Reuters

Obfuscation and impunity continue to characterize the coalition’s airstrike campaign. The coalition rarely identifies which country carries out an airstrike, although the vast majority are Saudi and Emirati, officials say. In July, King Salman of Saudi Arabia issued an order lifting “all military and disciplinary penalties” for Saudi troops fighting in Yemen, an apparent amnesty for possible war crimes.

Over the summer, as Emirati warplanes pounded the Red Sea port of Hudaydah, General Votel and the defense secretary at the time, Jim Mattis, held at least 10 phone calls or video conferences with Saudi and Emirati leaders, urging them to show restraint, a senior American military official and a senior Western official said.

At least one of the conferences involved Mohammed bin Zayed, the crown prince of Abu Dhabi and the effective leader of the United Arab Emirates.

“The Saudis are decent partners,” Gen. C.Q. Brown Jr., a former top commander of American air forces in the Middle East, said in an interview. “And sometimes our partners don’t always do things we would expect.”

Short of halting all weapons sales, critics say the United States could pressure the Saudis by curtailing its assistance to the air war. Hundreds of American aviation mechanics and other specialists, working under Defense Department contracts, keep the Saudi F-15 fleet in the air. In 2017, Boeing signed a $480 million contract for service repairs to the fleet.

But after the departure of Mr. Mattis, who resigned last week, the Defense Department will be helmed by Patrick M. Shanahan, an arms industry insider. Mr. Shanahan, the acting defense secretary as of Jan 1., spent more than three decades at Boeing, the F-15 manufacturer which has earned further billions from lucrative service contracts in Saudi Arabia.

Pentagon officials said that in his current job as deputy defense secretary, Mr. Shanahan had recused himself from decisions involving Boeing.

Daniel L. Byman, a professor at Georgetown University’s School of Foreign Service, said that a more robust policy toward Saudi airstrikes would not just be good for Yemeni civilians — it would also help the Saudis.

“This war has been a strategic disaster for the Saudis,” he said. The airstrikes have shown no sign of defeating the Houthis, and the Houthis’ foreign ally, Iran, has gained from Saudi Arabia’s clumsy prosecution of the war.

“The United States needs to use its power to promote peace and stability in Yemen,” Mr. Byman said. “And it needs to protect its allies from themselves.”